patricia-trie | 易学教程

Significance of the term “Radix” in Radix Tree

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问题 While it is hard to find an unanimous definition of "Radix Tree", most accepted definitions of Radix Tree indicate that it is a compacted Prefix Tree. What I'm struggling to understand is the significance of the term "radix" in this case. Why compacted prefix trees are so named (i.e. Radix Tree) and non-compacted ones are not called Radix Tree? 回答1: Wikipedia can answer this, https://en.wikipedia.org/wiki/Radix: In mathematical numeral systems, the radix or base is the number of unique digits

Determine if one string is a prefix of another

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问题 I have written down a simple function that determines if str1 is a prefix of str2. It's a very simple function, that looks like this (in JS): function isPrefix(str1, str2) // determine if str1 is a prefix of a candidate string { if(str2.length < str1.length) // candidate string can't be smaller than prefix string return false; var i = 0; while(str1.charAt(i) == str2.charAt(i) && i <= str1.length) i++; if(i < str1.length) // i terminated => str 1 is smaller than str 2 return false; return true

Confusion regarding PATRICIA [closed]

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问题 Closed . This question is opinion-based. It is not currently accepting answers. Want to improve this question? Update the question so it can be answered with facts and citations by editing this post. Closed 4 years ago . According to points 3 and 4 of libstdc++ documentation, PATRICIA tries have two types of nodes: A (PATRICIA) trie is similar to a tree, but with the following differences: It explicitly views keys as a sequence of elements. E.g., a trie can view a string as a sequence of

Confusion regarding PATRICIA [closed]

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According to points 3 and 4 of libstdc++ documentation , PATRICIA tries have two types of nodes: A (PATRICIA) trie is similar to a tree, but with the following differences: It explicitly views keys as a sequence of elements. E.g., a trie can view a string as a sequence of characters; a trie can view a number as a sequence of bits. It is not (necessarily) binary. Each node has fan-out n + 1, where n is the number of distinct elements. It stores values only at leaf nodes. Internal nodes have the properties that A) each has at least two children, and B) each shares the same prefix with any of its

python implementation of patricia tries

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问题 Looking around for python implementations of tries just so that I can understand what they are and how they work, I came across Justin Peel's patricia trie and found it very instructive: it's straightforward enough for one as new as I am to play around with it and learn from it. However there's something I think I'm not understanding: using Justin's class patricia() thus: >>> p = patricia() >>> words = ['foo','bar','baz'] >>> for x in words: ... p.addWord(x) I get a trie as a dictionary

python implementation of patricia tries

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Looking around for python implementations of tries just so that I can understand what they are and how they work, I came across Justin Peel's patricia trie and found it very instructive: it's straightforward enough for one as new as I am to play around with it and learn from it. However there's something I think I'm not understanding: using Justin's class patricia() thus: >>> p = patricia() >>> words = ['foo','bar','baz'] >>> for x in words: ... p.addWord(x) I get a trie as a dictionary looking like this: >>> p._d {'b': ['a', {'r': ['', {}], 'z': ['', {}]}], 'f': ['oo', {}]} addWord() and

Prefix search in a radix tree/patricia trie

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问题 I'm currently implementing a radix tree/patricia trie (whatever you want to call it). I want to use it for prefix searches in a dictionary on a severely underpowered piece of hardware. It's supposed to work more or less like auto-completion, i. e. showing a list of words that the typed prefix matches. My implementation is based on this article, but the code therein doesn't include prefix searches, though the author says: [...] Say you want to enumerate all the nodes that have keys with a

Are there any radix/patricia/critbit trees for Python?

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I have about 10,000 words used as a set of inverted indices to about 500,000 documents. Both are normalized so the index is a mapping of integers (word id) to a set of integers (ids of documents which contain the word). My prototype uses Python's set as the obvious data type. When I do a search for a document I find the list of N search words and their corresponding N sets. I want to return the set of documents in the intersection of those N sets. Python's "intersect" method is implemented as a pairwise reduction. I think I can do better with a parallel search of sorted sets, so long as the

Implementing a Patricia Trie for use as a dictionary

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I'm attempting to implement a Patricia Trie with the methods addWord() , isWord() , and isPrefix() as a means to store a large dictionary of words for quick retrieval (including prefix search). I've read up on the concepts but they just aren't clarifying into an implementation. I want to know (in Java or Python code) how to implement the Trie, particularly the nodes (or should I implement it recursively). I saw one person who implemented it with an array of 26 child nodes set to null/None. Is there a better strategy (such as treating the letters as bits) and how would you implement it? Someone

What is the difference between trie and radix trie data structures?

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Are the trie and radix trie data structures the same thing? If they are same, then what is the meaning of radix trie (AKA Patricia trie)? Ivaylo Strandjev A radix tree is a compressed version of a trie. In a trie, on each edge you write a single letter, while in a PATRICIA tree (or radix tree) you store whole words. Now, assume you have the words hello , hat and have . To store them in a trie , it would look like: e - l - l - o / h - a - t \ v - e And you need nine nodes. I have placed the letters in the nodes, but in fact they label the edges. In a radix tree, you will have: * / (ello) / * -